From d5466d1fdac927bc569ae2249cd3a2fa84fecf6a Mon Sep 17 00:00:00 2001 From: DarkSun Date: Fri, 11 Dec 2020 05:03:23 +0800 Subject: [PATCH] =?UTF-8?q?=E9=80=89=E9=A2=98[tech]:=2020201209=20Program?= =?UTF-8?q?=20a=20simple=20game=20with=20Elixir?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit sources/tech/20201209 Program a simple game with Elixir.md --- ...01209 Program a simple game with Elixir.md | 141 ++++++++++++++++++ 1 file changed, 141 insertions(+) create mode 100644 sources/tech/20201209 Program a simple game with Elixir.md diff --git a/sources/tech/20201209 Program a simple game with Elixir.md b/sources/tech/20201209 Program a simple game with Elixir.md new file mode 100644 index 0000000000..8304970ff0 --- /dev/null +++ b/sources/tech/20201209 Program a simple game with Elixir.md @@ -0,0 +1,141 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (Program a simple game with Elixir) +[#]: via: (https://opensource.com/article/20/12/elixir) +[#]: author: (Moshe Zadka https://opensource.com/users/moshez) + +Program a simple game with Elixir +====== +Learn Elixir by programming a "guess the number" game and comparing the +language against ones you know. +![A die with rainbow color background][1] + +To you learn a new programming language, it's good to focus on the things most programming languages have in common: + + * Variables + * Expressions + * Statements + + + +These concepts are the basis of most programming languages. Because of these similarities, once you know one programming language, you can start figuring another one out by recognizing its differences. + +Another good tool for learning a new language is starting with a standard program. This allows you to focus on the language, not the program's logic. We're doing that in this article series using a "guess the number" program, in which the computer picks a number between one and 100 and asks you to guess it. The program loops until you guess the number correctly. + +The "guess the number" program exercises several concepts in programming languages: + + * Variables + * Input + * Output + * Conditional evaluation + * Loops + + + +It's a great practical experiment to learn a new programming language. + +### Guess the number in Elixir + +The [Elixir][2] programming language is a dynamically typed functional language designed for building stable and maintainable applications. It runs on top of the same virtual machine as [Erlang][3] and shares many of its strengths—but with slightly easier syntax. + +You can explore Elixir by writing a version of the "guess the number" game. + +Here is my implementation: + + +``` +defmodule Guess do +  def guess() do +     random = Enum.random(1..100) +     IO.puts "Guess a number between 1 and 100" +     Guess.guess_loop(random) +  end +  def guess_loop(num) do +    data = IO.read(:stdio, :line) +    {guess, _rest} = Integer.parse(data) +    cond do +      guess < num -> +        IO.puts "Too low!" +        guess_loop(num) +      guess > num -> +        IO.puts "Too high!" +        guess_loop(num) +      true -> +        IO.puts "That's right!" +    end +  end +end + +Guess.guess() +``` + +To assign a value to a variable, list the variable's name followed by the `=` sign. For example, the statement `random = 0` assigns a zero value to the `random` variable. + +The script starts by defining a **module**. In Elixir, only modules can have named functions in them. + +The next line defines the function that will serve as the entry point, `guess()`, which: + + * Calls the `Enum.random()` function to get a random integer + * Prints the game prompt + * Calls the function that will serve as the loop + + + +The rest of the game logic is implemented in the `guess_loop()` function. + +The `guess_loop()` function uses [tail recursion][4] to loop. There are several ways to do looping in Elixir, but using tail recursion is a common one. The last thing `guess_loop()` does is call _itself_. + +The first line in `guess_loop()` reads the input from the user. The next line uses `parse()` to convert the input to an integer. + +The `cond` statement is Elixir's version of a multi-branch statement. Unlike `if/elif` or `if/elsif` in other languages, Elixir does not treat the first nor the last branch in a different way. + +This `cond` statement has a three-way branch: The guess can be smaller, bigger, or equal to the random number. The first two options output the inequality's direction and then tail-call `guess_loop()`, looping back to the beginning. The last option outputs `That's right`, and the function finishes. + +### Sample output + +Now that you've written your Elixir program, you can run it to play the "guess the number" game. Every time you run the program, Elixir will pick a different random number, and you can guess until you find the correct number: + + +``` +$ elixir guess.exs +Guess a number between 1 and 100 +50 +Too high +30 +Too high +20 +Too high +10 +Too low +15 +Too high +13 +Too low +14 +That's right! +``` + +This "guess the number" game is a great introductory program for learning a new programming language because it exercises several common programming concepts in a pretty straightforward way. By implementing this simple game in different programming languages, you can demonstrate some core concepts of the languages and compare their details. + +Do you have a favorite programming language? How would you write the "guess the number" game in it? Follow this article series to see examples of other programming languages that might interest you. + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/20/12/elixir + +作者：[Moshe Zadka][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/moshez +[b]: https://github.com/lujun9972 +[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/dice_tabletop_board_gaming_game.jpg?itok=y93eW7HN (A die with rainbow color background) +[2]: https://elixir-lang.org/ +[3]: https://www.erlang.org/ +[4]: https://en.wikipedia.org/wiki/Tail_call